On a technical level, Apple can comply with the U.S. Federal Bureau of Investigation's (FBI) request for help in accessing an iPhone used by Syed Rizwan Farook, one of the people accused of killing 14 in California two months ago, security experts said Wednesday.
"I believe it is technically feasible for Apple to comply with all of the FBI's requests in this case," said Dan Guido, the co-founder and CEO of Trail of Bits, a New York City-based security firm, in a Wednesday post on his firm's blog. "On the iPhone 5C, the passcode delay and device erasure are implemented in software and Apple can add support for peripheral devices that facilitate PIN code entry."
Essentially, what the FBI has asked Apple to do -- with a federal magistrate's concurrence -- was to make it possible for investigators to brute-force the passcode on the iPhone 5C by subverting iOS's limitations on entering such codes, as well as removing the auto-wipe feature, triggered when several incorrect passcodes are entered. On Farook's iPhone 5C, which is running iOS 9, each successive incorrect entry enforces a delay until the next can be punched in.
The result: The FBI has been stymied, afraid that entering wrong passcodes -- which must be tapped in by hand -- would take too long, but more importantly, quickly wipe the iPhone clean.
"In plain English, the FBI wants to ensure that it can make an unlimited number of PIN guesses, that it can make them as fast as the hardware will allow, and that they won't have to pay an intern to hunch over the phone and type PIN codes one at a time for the next 20 years," said Guido.
Guido initially argued that the same request would be moot on newer iPhones -- any model equipped with the Apple-designed A7 SoC (system on a chip), which was first used in 2013's iPhone 5S.
The barrier would be the Secure Enclave (SE), a co-processor fabricated as part of the A7. The Secure Enclave is not accessible to iOS, so any changes Apple might make to its mobile operating system -- the gist of what the FBI's asking Apple to do -- would be worthless.
SE is responsible for processing the fingerprint data acquired by the Touch ID sensor, and also encrypts the device and its contents with a unique key pre-set during manufacturing that is "entangled," or combined, with the device's unique ID (UID) as well as the user-set passcode on the lock screen. Apple does not know or have a record of the key embedded in the Secure Enclave.
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